Tank destroyer
A tank destroyer, tank hunter or tank killer is a type of armoured fighting vehicle, predominantly intended for anti-tank duties. They are typically armed with a direct fire artillery gun, also known as a self-propelled anti-tank gun, or missile launcher, also called an anti-tank missile carrier. The vehicles are designed specifically to engage and destroy enemy tanks, often with limited operational capacities beyond its intended role.
While tanks are designed for front-line combat, combining operational mobility and tactical offensive and defensive capabilities and performing all primary tasks of the armoured troops, the tank destroyer is specifically designed to take on enemy tanks and other armoured fighting vehicles. Many are based on a tracked tank chassis, while others are wheeled.
Since World War II, gun-armed powerful tank destroyers have fallen out of favor as armies have favored multirole main battle tanks. However, lightly armoured anti-tank guided missile carriers are commonly used for supplementary long-range anti-tank work. The resurgence of expeditionary warfare in the first two decades of the 21st century has seen the emergence of gun-armed wheeled vehicles, sometimes called "protected gun systems", which may bear a superficial resemblance to tank destroyers, but are employed as direct fire support units typically providing support in low-intensity operations, as was done in wars in Iraq and Afghanistan.
World War II
Dedicated anti-tank vehicles made their first major appearance in the Second World War as combatants developed effective armoured vehicles and tactics. Some were little more than stopgap solutions, mounting an anti-tank gun on a tracked vehicle to give mobility, while others were more sophisticated designs. An example of the development of tank destroyer technology throughout the war is the Marder III and Jagdpanzer 38 vehicles, which were very different in spite of being based on the same chassis: Marder was straightforwardly an anti-tank gun on tracks, whereas the Jagdpanzer 38 traded some firepower for better armour protection and ease of concealment on the battlefield.Except for most American designs, all tank destroyers were turretless vehicles with fixed or casemate superstructures. When a tank destroyer was used against enemy tanks from a defensive position such as by ambush, the lack of a rotating turret was not particularly critical, while the lower silhouette was highly desirable. The turretless design allowed accommodation of a more powerful gun, typically a dedicated anti-tank gun that had a longer barrel than could be mounted in a turreted tank on the same chassis. The lack of a turret increased the vehicle's internal volume, allowing for increased ammunition stowage and crew comfort. Eliminating the turret let the vehicle carry thicker armour, and also let this armour be concentrated in the hull. Sometimes there was no armoured roof to keep the overall weight down to the limit that the chassis could bear. The absence of a turret meant that tank destroyers could be manufactured significantly cheaper, faster, and more easily than the tanks on which they were based, and they found particular favor when production resources were lacking.
Germany
The first German tank destroyers were the Panzerjäger, which mounted an existing anti-tank gun on a convenient chassis for mobility, usually with just a three-sided gun shield for crew protection. For instance, 202 obsolete Panzer I light tanks were modified by removing the turret and were rebuilt as the Panzerjäger I self-propelled 4.7 cm PaK. Similarly, Panzer II tanks were used on the Eastern Front. Captured Soviet anti-tank guns were mounted on modified Panzer II chassis, producing the Marder II self-propelled anti-tank gun. The most common mounting was a German anti-tank gun on the Czech Panzer 38 chassis; this combination was deemed the Marder III. The Panzer 38 chassis was also used to make the Jagdpanzer 38 casemate style tank destroyer. The Panzerjäger series continued up to the equipped Nashorn.German tank destroyers based on the Panzer III medium tank and later German tanks had more armour than their tank counterparts. One of the more successful German tank destroyers was designed as a self-propelled artillery gun, the Sturmgeschütz III. Based on the Panzer III tank chassis, the Sturmgeschütz III was originally fitted with a short barreled low-velocity howitzer-like gun, and was assigned to the artillery arm for infantry fire support as an assault gun. Later, after encountering Soviet tanks, it was refitted with a comparatively short-barreled high-velocity anti-tank gun, usually with a muzzle brake, enabling it to function as a tank destroyer. The Sturmgeschütz III from its 1938 origin used a new casemate-style superstructure with an integrated design, similar to the later Jagdpanzer vehicle designs' superstructure, to completely enclose the crew. It was employed in infantry support and offensive armoured operations as well as in the defensive anti-tank role. The StuG III assault gun was Germany's most-produced fully tracked armoured fighting vehicle during World War II, and second-most produced German armoured combat vehicle of any type after the Sd.Kfz. 251 half-track.
Although early German Panzerjägers carried more effective weapons than the tanks on which they were based, they were generally lacking in protection for the crew, having thinly armoured open-topped superstructures. The "open-topped" design format of the Panzerjäger vehicles was succeeded by the Jagdpanzer, which mounted the gun in true casemate-style superstructures, completely enclosing the crew compartment in armour usually integral to the hull. The first of these Jagdpanzers was the 70-ton Ferdinand, based on the chassis, hulls, and drive systems of ninety-one Porsche VK4501 heavy tanks, and a long-barreled 88 mm cannon mounted in an added casemate. Like the Panzerjägers before it, the Ferdinand received additional armour for the gun crew, but also completely enclosed gun and crew within the added casemate, as later purpose-built Jagdpanzers would. However, the Ferdinand was mechanically unreliable and difficult to maneuver, and once all ninety-one unturreted "Porsche Tiger" hulls/drive systems were converted, no more were built. The German Army had more success with the Jagdpanther. Introduced in mid-1944, the Jagdpanther, of which some 415 examples were produced, was considered the best of the casemate-design Jagdpanzer designs. It featured the same powerful PaK 43 88 mm cannon used on the unwieldy Elefant, now fitted to the chassis of the medium Panther tank, providing greatly improved armour-penetrating capability in a medium-weight vehicle.
Facing an increasingly defensive war, the German Army turned to larger and more powerfully armed Jagdpanzer designs, and in July 1944 the first Jagdtiger rolled off the production line; it was the heaviest German armoured fighting vehicle to go into active service. The Jagdtiger was based on the Tiger II heavy tank and featured a very large 128 mm PaK 44 cannon and heavy armour protection. Only 88 Jagdtiger vehicles were produced, barely matching the total number of the earlier Ferdinand/''Elefant'' vehicles. They were first deployed to combat units in September 1944.
The decision to use a casemate-style superstructure for all tank destroyers had the advantage of a reduced silhouette, allowing the crew to more frequently fire from defilade ambush positions. Such designs were also easier and faster to manufacture and offered good crew protection from artillery fire and shell splinters. However, the lack of a rotating turret limited the gun's traverse to a few degrees. This meant that the driver normally had to turn the entire tank onto its target, a much slower process than simply rotating a powered turret. If the vehicle became immobilized due to engine failure or track damage, it could not rotate its gun to counter opposing tanks, making it highly vulnerable to counterfire. This vulnerability was exploited by opposing tank forces. Even the largest and most powerful of German tank destroyers were found abandoned on the field after a battle, having been immobilized by one or more hits by high explosive or armour-piercing shells to the track or front drive sprocket.
Italy
The most famous Italian tank destroyer of the Second World War was a self-propelled gun. The Semovente da 75/18, based on the M13/40 frame, was developed to support front-line infantry, and therefore had fixed armament: a 75 mm gun in casemate. However, thanks to its low height and the caliber of its gun the 75/18 also had good results in anti-tank combat, fighting against British and American units. After the Armistice of 1943, the 75/18 remained in use by German forces.Built on the same frame, the Semovente da 105/25 was equipped with a 105 mm gun and known as "bassotto" due to its lower height. As manufacturing began in 1943, the 105/25 was used by German forces. A further development was the Semovente da 75/46, which had a longer gun than the 75/18 and inclined armour 100 mm thick, making it similar to Sturmgeschütz III. Only 11 of these were manufactured. Before the Semovente da 75/18, the L40, built on an L6/40 light tank chassis, saw action in Africa and in Russia, but with disappointing results.
Japan
The Type 1 Ho-Ni I was the first self-propelled gun design of the Imperial Japanese Army. They were meant to be self-propelled artillery and tank destroyers for armoured divisions. The plan was for the Type 1 Ho-Ni I gun tank to form part of a fire support company in each of the tank regiments. The Type 1 Ho-Ni I was developed by using the existing Type 97 Chi-Ha medium tank chassis and engine, and replacing the gun turret with a Type 90 75 mm field gun mounted in an open casemate with frontal and side armour only. They entered service in 1942 and were first deployed in combat at the Battle of Luzon in the Philippines in 1945. Some were used in static entrenched positions.A variant, known as the Type 1 Ho-Ni II mounted a Type 91 105 mm howitzer and had a slightly changed superstructure as far as the side armor with re-positioned observation visors. Production began in 1943, with only 54 completed.
The other variant produced was the Type 3 Ho-Ni III, which mounted a Type 3 75 mm tank gun in a completely enclosed armored casemate to address the issue of crew protection in close combat. The welded superstructure had sloped armour and the gun mount had additional stamped armour plate. The total number produced of all three types in the Ho-Ni series were 111 units. Most of the Ho-Ni units were retained within the Japanese home islands to form part of the defenses against the projected American invasion, and did not see combat before the surrender of Japan.
The Type 2 Ho-I Gun tank used the Type 1 Chi-He medium tank chassis. It was designed as a self-propelled howitzer, mounting a short barreled Type 99 75 mm gun to provide close-in fire support. For deployment, the gun tank was intended to be used in a fire support company for each of the tank regiments. No Type 2 Ho-I gun tanks are known to have engaged in combat prior to Japan's surrender. The prototype was built in 1942 and 31 units were produced in 1944.
The Type 4 Ho-Ro self-propelled artillery used a modified Type 97 chassis. On to this platform, a Type 38 150 mm howitzer was mounted. The main gun could fire Type 88 APHE rounds and HEAT rounds. Given its breech loader, the maximum rate of fire was only 5 rounds per minute. The gun's elevation was restricted to 30 degrees by the construction of the chassis. Other design issues included the fact that although the gun crew was protected by a gun shield with armour thickness of 25 mm at the front, the shield only extended a very short distance on the sides; leaving the rest of the sides and back exposed. They were rushed into service, deployed and saw combat during the Philippines Campaign in the last year of World War II. Remaining units were deployed to Okinawa in ones and twos for island defense during the Battle of Okinawa, but were severely outnumbered by American artillery.